White-Knuckled Prosociality: Loneliness increases willingness to exert effort to benefit others

Loneliness, or perceived social isolation, motivates individuals to foster their relationships while remaining vigilant to potential social threats. Lonely individuals must interpret the social cues they receive from others and respond accordingly by engaging in affiliative behaviors while also identifying and managing threats. Prosocial acts – or voluntary actions meant to benefit others – are one type of behavior that can help lonely individuals reaffiliate. Loneliness has been linked to differences in prosocial behaviors. However, this relationship has mainly been investigated using self-report measures that ask respondents to imagine their own behavior in hypothetical scenarios. Here, we utilized a physical effort prosocial decision-making experimental task to investigate whether loneliness influences willingness to exert physical effort to benefit others. We also explore whether this relationship differs in contexts of potential gain compared to potential loss and is moderated by participants’ resting parasympathetic nervous system (PNS) activity as a physiological marker of variability in individuals’ ability to regulate competing social motivations. In a sample of 80 U.S. undergraduate students, we find lonelier individuals are more likely to choose to exert effort to benefit someone else both to earn rewards and to avoid punishments. Resting cardiac PNS activity did not moderate the association between loneliness and prosocial behavior. These findings indicate loneliness increases effortful prosocial behavior, which is in line with theoretical frameworks positing prosocial actions as a tool for lonely individuals to foster connection and reaffiliation with others. Implications for our understanding of loneliness as a driver of social behavior are discussed.